I feel pretty stupid. I should know this stuff. I was asking some stupid questions and found out that I might have not been charging my system the best way possable. I contacted some people that have way more experiance doing this sort of thing. Big charging system's like RV's and pleasure boat's with large multi battery bank's. I didnt know that Optima's have a completey diffrent charging regimen than other AGM battery's, Gell and flooded batterys aslo have a diffrent charging regimen. Unless you have a SMART voltager regulator/charger your AGM batterys will never reach a full 100% charge. A alternator has a internat or external voltage regulator but it throw's amps/and volts at what ever the batterys will accept and not what they need. Example a to re-charge a AGM battery back to 100% it will need a "Bulk charge" of 14.6 volts and lets say 40 amps for 45 min's then 14.3 volts at 30 amps for 20 min's then a float charge for 13.3 volts at 10 amp's for 5 min's These #'s are just a example but you get the point. A regular alternator does not charge the batterys back like this. This is why I was only getting a full charge after my boat was connected to a trickle charger for some time 3-4 day's. My HO alternator wasnt charging me back to 100% not because it didnt have enough power to do so but because it didnt know how. I was only getting about a 50% charge from my alternator The charge needs to be in a step and set process. Traditional flooded car batterys/golf carts dont need this type of chargeing regimen.

Another thing I found out, I think I need a larger 210 amp alternator.

I havent done a test but Im guessing my boat is pulling 50-70 amp's playing the system at mid to high volume. Ill do some testing to find out for sure. But traditionaly we park and play the system the batterys get low and I fire up the boat and start charging the system. This needs to be done for 2 reason's #1 If I let the batterys get to low my alternator will melt itself down trying to re-charge my battery's so I fire up just to prevent the voltage drop into levels that will kill my alternator. #2 Its not good for your equipment to try working at high volumes with low voltage, they get hot ect. So the scenario go's You park. You play. Your batterys get low and you fire up to charge your batterys back. Your still playing. All your doing is maintaining a flat battery, Your HO alternator is throw 70 amps continously, well guess what thats what my system is using 50-70 amps. So Im not charing 1 bit. Or if you push it you will do the alternator melt down. Now a larger 210 alternator could maintain my system and throw 50-70 amps back at the batterys all while playing and not going into melt down mode. but Like I said unless you have a smart regulator or charger it dosent even matter you can have a 310 amp alternator and you still not gonn hit 100% charge. Alot of the smart charger/regulators have a heet probe that measures the alternators temp at the case. The more amp's you make the more heet your gonna create. The smart regulators/alternators will or can cut it's output in 1/2 untill the temp drops so it dosnt have a melt down.

Now the bad new's This type of set up is not cheep Like $2000 or more and Im gonna need to upgrade to a dule 1/2 inc pully belt's to handle the extra strain the 210 alternator is gonna pull.

Why don't you buy a decent dual or triple bank MARINE battery charger. They are more sophisticated than that thing and are ignition proof and waterproof. Mine is 20 amp, and will charge two at 10 amp or switch all the current to the bank that needs it, charge gel, spiral, lead acid, mr fusion, whatever. There are much bigger ones available, I only run 2 or 3 batts.

If I were going to run a huge system all day, I would buy a Honda generator and an extension cord, put it on the dock or the beach. You're tied up anyway, right?

Sounds like he's more concerned with onboard charging(alternator, etc). I agree the 4 bank would do a better job charging overnight and in storage. I'm looking for a similar solution for charging while on the lake. I used to run an isolator, which doesn't step charge and was also limited by a 25-30 Amp capacity. No luck so far.

Thanks for the post, Grant. I picked up a few bits of alternator knowledge today. Kind of off-topic, but kind of not..

I picked up a HO alternator for pretty cheap. It was sold to me as a used (+/- 10,000 miles) Summit Racing 160amp self exciting.

So I took it to a Starter/Alternator shop and the guy explained the load tests as he performed them. What was interesting was being able to see the current the alternator would deliver at the different voltage levels. For instance, the tests began at 14.4 volts and the alternator delivered 35amps. As he added a load to the system, the voltage would drop and the alternator would increase it's output to match the increased load. My alternator, while at 12.6 volts only delivered a measly 105 amps. Under full load (about 9 volts) the Alternator maxed at 140 amps. Yep, my 160 amp alternator turned into a weak 140amp. The guy said, "it'll still do ok.. I don't know if it'll power a 70 amp load very well."

Apparently the current the alternator delivers at 12.6 volts is quite important. How often do you draw your system down below 12v? Well, if the system is at 12.6v, and my stereo draws 70amps, ~20amps for running the boat, that gives me 15 left over for charging. But it's a 140 amp alternator! Well, Yes, at 9.5 volts my alternator will deliver 140amps, but I'll never run my system that low (hopefully), so I'll never be able to take advantage of those last 35 amps. So basically, I have a ~105 amp alternator.

He pulled a new HO 150amp out of the box, and it was putting out 135 at 12.6 volts. While putting out a true 150 amps Max, and 45-55 at 14.4.

Moral of my story, an Alternator is only as good as the current it'll provide in the 12v range. You can have a 300amp alternator, but if it only provides 70amp at 12v, how High-Output is it really?

Grant, Who gave you this information? Don't feel stupid, I don't think the information is 100% correct.

Heres a link to the Optima Spec Sheet for the D31m, optimabatteriesD31MI think whoever told you this was thinking of 100% discharge, but I don't think you've ever been that close(100% discharge is basically a brand new battery with no voltage reading at all) Your current method should suffice, only adding a trickle charge during the week to peak the battery bank.

If I was you I wouldn't worry about getting the maximum charge into/out of your batteries.

I have seen very few RV's that have a decent battery / charging system. RV's generally have propane appliances, including the refrigerator, so all they need battery for are the lights.

A lot of boats, on the other hand, prefer not to use propane due to the explosion hazards so the refrigeration is often 12 volts. Sailboats especially will be set up for extended voyages where they live or die off their batteries.

A cruiser wants and needs to be able to start the engine up, run it for an hour and be all set for another day or two. They may need to do this for months so they need a very efficient system that treats the batteries well.

You don't have that situation. I just can't imagin that getting that last 5% of charge on your batteries matters that much to you. When you are pulling a hundred amps out of the battery you are talking about another few minutes of run time.

What is critical for you is that the alternator be able to provide a comfortable margin over the "average" power draw when you are running the engine for an "average" amount of time.

Don't worry that the amps might draw a peak of 300 amps, the average will be a lot less. Do worry that time spent at idle will decrease the output of the alternator and thus lower its average output.

If the alternator was properly designed it should be able to crank out its rated current all day long and not melt down. I do worry about some of the alternator mods where they tweak them to get more output as they may not tweak the cooling an equal amount.

As for the battery charging:

The standard alternator operates on a voltage/current curve. As the voltage increases, the current out decreases. If the battery is low, 12.5 volts or less, the alternator should be putting out full current. As the battery voltage raises the current is reduced. Under "nominal" load the voltage would settle around 13.2 volts. Under light load the the voltage might go up to 14.2 volts. At this point the alternator should be putting out its minimum current (which is typically not zero!)

A battery, on the other hand, would like to see a constant current applied until the voltage reached 14.2 volts, then have it reduced to 13.2 volts. This will fully charge the battery in the minimum amount of time. To get this type of charge you will need a "smart" voltage regulator, which requires an alternator with an external regulator.

But as I said before, you don't need it unless your objective is to charge a massive battery bank so you can run the stereo with the engine off for the maximum amount of time.

Grant, do you ski with this boat, or do you just show off your stereo?

My recommendation is to add a second alternator rather than replacing the alternator with one twice as large. Redundency is always nice, the load on the belt(s) will be less and two alternators will provide twice as much cooling as one.

Another issue you need to worry about is the wear and tear on the batteries. A good rule of thumb is that if you want to maximize the battery life then don't charge at a rate of more than 10% of the batteries amp-hour capacity. If you have a 100 amp-hour battery don't force more than 10 amps at it. You really don't want your alternator forcing 100 amps into the battery, it will destroy it in short order.

If you are not worried about getting the last 5% of your batteries then don't worry about the actual charging regimen. You want to make sure that the alternator can supply the amplifiers, run everything on the boat (including ballast pumps) and still have 10 amps left over to charge batteries.

Mike yes they say you run the higher charge cables to a real to avoid the 35 amp chke the Cd puts on your alternators output.

Craig: Yes I feal your Alternator pain, And just thing the # you were seeing were the BEST your ever gonna see. Its only gonna get weaker when you throw it in your boat. The quality and length of the wire and the amount of power your boat consumes is all gonna make your #'s even worse. Rod A few thing's

For me parking and playing with out having to keep the boat running is what this whole thing is about. If you keep your boat running all the time and never play with out the motor turned off then all of this is a mute point

Where did you here that you shouldnt charge your AGM a batterys at more than 10% of its amp hrs. I have been told you can and should charge at a much higher rate, Example a Optima with 55 amp hrs likes to get a 20 amp charge. Mabey this is the "Bulk charge" experts are talking about. My old system had 255 amp hrs. Lets say my alternator was working at 100% that's 27amp hrs per optima in a best case seniero sertanly not a over kill situation. Now take into concideration your boat is running and its pulling some amps and your stereo is still running and its pulling amp's so that magical 27 amp's per battery we were talking earlyer is about is now more like 10-15 amp's and that's assuming your alternator is putting out full power 135-150 amp's. I say a GOOD "150" amp alternator pushes between 70 130 amps.

My new battery system is 428 amp hrs. Thats a pretty large battery bank for a ski boat. Not alot of people are pushing banks that large.

Think of the way we use our battery power like the way large sail boat's use there power. But think of it more like this, a sail boat would use its battery/amp hrs over several day's we use it in several hr's.

Grant> I think its time to stop the 'small' ideas-time to get an on board gas powered generator. I havent done much research on them but I do know that some people run a battery bank and have a gas generator that runs their whole house! No, not a floating house, but more like a 3 bedroom 2 bath concrete foundation house! Im sure there is a way that you can quite down the generator so that you cannot hear it much even when your boat is not running. You can have the generator get its gas from your boat gas tank. What stops you from going that route? I believe this is the 'ultimate' setup. Alternator s are not strong enough to charge a large battery bank, but they are strong enough to 'maintain'. I believe that your being modest on your amperage that you will pull with you stereo at full throttle. How many did mine pull at each stab? Something like 130 amps Thru 0 guage wire? I would think yours will pull close to the same. Another thing that I just thought of is solar power. WE are always taking our boats out in the sun- hardly ever when its not sunny out. I would imagine that it would be costly but if anyone can find a place to mount a solar panel and make something trick it you be you! Maybe a solar panel on top of the tower? On top of the gunnels around the windshield area? Can you fit a small panel there? For someone who mounds led's in crazy ass places it shouldnt be hard to find a place to mount a panel that will give you battery power for free!

I say you gut a Prius, take the batteries and attach some paddle wheels that can generate extra juice while you are cruising along. I am sure you can also fit the engine in one of the side compartments and run the quiet, gas efficient motor to generate enough juice for some additional amplifiers... With this set up you can use the diamond lane on the way to the delta! I have a few more ideas but I think this is enough to get you started.

#1 Add a Nuclear reactor #2 Throw a power coard to shore #3 Make special tow along boat that hauls a generator #4 Install a generator in your boat #5 Solar power Last but not least #6 the system you have now is fine why do you want to do anything.

Psyclone: I disagree. I have got some great advice, There is lots of lurkers out there that are way smarter than most experts. Once in a while they come out of the wood work and help out. You would be suprised at who's out there.

I have the Balmar 210 alt . and a little different wiring system than Grant is talking about but it does the same thing also Jerry Pontes boat has it too . I think Grant is right on the money on his new way of thinking . Its not new Kustom Kar has been usuing it for a few years .The first thing Christopher Bishop told me a year ago when I walked in his shop was with out the Balmar system all I woud get is a surface charge while the boat was running and it would need to be deep charged with a charger to get the batterys to max capacity. If your going to run a big system this is good advice .

We need to keep things in perspective here. Joe, Grant, and a few other's are in a completely different realm when it comes to power demand on the boat. I will call these "No Excuses" systems. These guys are running systems in excess of 4kW (4 kilowatts, 4,000 watts). When you get to that level the stereo's electrical system starts to dwarf the boat's electrical system.

Most guys like me running 2kW +/- systems can squeak by with a 100+ amp stock or traditional aftermarket alternator if you don't push things too hard.

Another aspect for this discussion is; How much horsepower are you giving up to run that big alt?

If you are running class A/B amps the electrical power to audio power conversion is done with about 50% efficiency. A typical alternator is probably 75% efficient and the belt running it probably 75% efficient as well. So all this means you need to put 4x horsepower to wattage. So 150 charging amps will cost you about 11hp. Does your boat have an extra 11hp?

This is the DDC Digital Duo Charge. Its a programable digital flow regulator and battery combiner. The wire is the Battery temp probe that mounts to the neg side of the battery bank and keeps track of the battery temp via the DDC. If the batterys get hot they can and will absorb more current then is good for them the temp senc makes sure they dont get over charged.

Hey Rod: more info I was told AGM battery's can take and like a 40 amp bulk charge.

I got my alternator in today "Wo" its a monster. I hope it fit's. This things looks seroius, Its got big power and ground post's at the back. Im gonna run a New 0-awg ground and power from the back of this to my bat's